Apple’s Tim Cook and Google’s Sundar Pichai were in attendance this weekend at the World Internet Conference in Wuzhen, China. There, they would have heard Chinese President Xi Jinping, in a letter read to delegates, again reassert the doctrine of cyber sovereignty, the idea that each country has the right to govern the Internet how it likes within its own borders.

Xi said the world should respect that sovereignty, foster a spirit of partnership, advance development, safeguard security, participate in governance, and share the benefits. “Building a community of common future in cyberspace has increasingly become the widespread common understanding of international society,” he said. “China’s door to the world will never close, but will only open wider.”

China this year codified the concept of cyber sovereignty into law. These and earlier rules have kept many prominent Western tech companies from operating in China, or severely crimped their operations in the Middle Kingdom. Facebook, Twitter and Netflix are all banished. Google pulled its search operations out of China in 2010, and its YouTube and Gmail programs are no longer accessible from within China. Crypto-currency Bitcoin is also banned.

China’s Alibaba is increasingly a competitor with U.S.-based Amazon on fronts that range from home shopping to cloud computing. Driven by an ecosystem that spans games, music and messaging, China’s Tencent now approaches Facebook in terms of market capitalization. And Baidu positions itself as a global market leader in artificial intelligence and driver-less cars, rivaling Google, among others.